This invention relates to a method for removing plutonium from the body and more particularly is directed toward a method for removing polymeric plutonium from hepatic tissue.
Continuing studies have been directed toward development of new approaches to the therapy of poisoning by both nonradioactive and radioactive metals. Considerable emphasis has been directed in the last several years toward the radioactive elements in view of the radiological health hazards they present. The ionizing radiations of the radioactive metals are of even greater concern than their chemical toxicity because of the risk of pathological changes and tumor induction from the radioactive ionizations. Compounds of toxic heavy metals are known to preferentially concentrate in various organs of the body. For example, plutonium introduced into the blood becomes selectively deposited mainly in the liver (as much as 30% to 90% of an administered amount of plutonium) and in the skeleton. Once the toxic metal has deposited within an organ its concentration may be only very slowly reduced, thereby increasing the potential for tumors and other radiation-induced damage. Plutonium deposited in the skeleton is of particular concern because of its high potential for inducing the formation of delayed osteogenic sarcomas. Plutonium deposited in the liver poses an additional problem, as a large fraction of the deposited plutonium which slowly leaves this organ may be translocated to bone surfaces, at which location its toxicity is much enhanced.
Previous techniques have employed the polyaminopolycarboxylic acid ethylenediaminetetraacetic acid (EDTA) as a chelating agent for removing toxic metals from animal tissue. More recently, a related polyaminopolycarboxylic acid, diethylenetriaminepentaacetic acid (DTPA) has been shown to have a greater ability to remove various heavy metals, particularly plutonium and other actinide elements. The use of these chelating agents, usually in the form of their calcium and/or sodium salts, for the removal of toxic metals is based on their ability to form stable, soluble, and readily excretable complexes with the metal ions in the tissues. They have proven valuable because they, in themselves, have a very low toxicity, are soluble, and resist degradation by tissue metabolites. However, a serious limitation to the use of chelating agents such as DTPA and EDTA is that they exist as charged, hydrated, lipid-insoluble anions in the blood plasma. These anions are unable to penetrate cellular membranes. Therefore, only extracellularly deposited metals are accessible for complexation by the chelating agent and subsequent removal from the body, whereas intracellularly deposited metals are not accessible to the chelating agent and therefore are not readily removed.
More recent attention, therefore, has been directed toward finding substances which will be effective in removing intracellularly deposited toxic metals, plutonium in particular. One substance which we have demonstrated as being effective in removal of additional plutonium, and in particular hepatic plutonium otherwise unavailable for chelation by DTPA, is the polysaccharide glucan derived from yeast cell walls. Glucan, however, is not totally satisfactory since glucan is insoluble and exhibits toxicity, factors which must be taken into account in the development of any practical therapeutic technique.
Therefore, it is an object of the present invention to provide a method for removing plutonium from the body.
It is another object of the present invention to provide a method for removing intracellularly deposited plutonium.
Another object of the present invention is to provide a method for removing plutonium from hepatic tissues.
It is another object of the present invention to provide a method for removing hepatic plutonium not removable by chelating agents alone.
Another object of the present invention is to provide a method for removing plutonium from hepatic tissues and from the body without translocating the plutonium to other tissues.